JP7126972B2 - Method for removing Sn and method for producing Pb - Google Patents

Description

This application relates to a Sn removal method and a Pb production method.

For example, in lead smelting, which manufactures product Pb from lead raw materials such as lead (Pb) slag generated in copper smelting, etc., tin (Sn) scum is generated by soda treatment of molten crude Pb metal. . Sn can be removed by collecting Sn scum (see, for example, Patent Document 1).

JP 2013-234356 A

However, when trying to collect Sn scum with a net, impurities such as Pb may be mixed into the Sn scum. If the Sn scum contains a large amount of impurities, the amount of the impurities may increase when the Sn scum leaching residue is repeated in the lead smelting process, which may increase the processing cost and deteriorate the yield.

In view of the above problems, an object of the present invention is to provide a method for removing Sn and a method for producing Pb that can suppress the amount of impurities mixed into Sn scum.

In one aspect, the method for removing Sn comprises a soda treatment step in which molten crude Pb metal is treated with soda in a Harris furnace; and a removing step of removing the Sn scum by scooping it with a second net having a mesh smaller than that of the first net.

The first net may have an opening of 3 mm to 5 mm, and the second net may have an opening of 1.5 mm or less. The Sn scum may be scooped by the second net after being scooped by the first net a plurality of times. The scum may be scooped multiple times with the first net, and the scum may be scooped with the second net after the scum is no longer scooped with the first net. The Sn content in the molten crude Pb metal may be 3 mass % or less during a period from scooping the Sn scum with the first net until scooping the Sn scum with the second net. The Pb content of the Sn scum scooped by the first net and the second net may be 20 mass % or less. The Sn grade of the molten crude Pb metal may be 3.0 mass % or more.

In one aspect, the method for producing Pb comprises producing Pb by performing an electrolysis step on refined Pb metal obtained by removing Sn from crude molten Pb metal by the method for removing Sn described above. Characterized by

According to the present invention, the amount of impurities mixed into Sn scum can be suppressed.

It is a figure explaining an example of the manufacturing process which manufactures product Sn and product Pb. It is a figure which illustrates a Harris treatment process.

Embodiments for carrying out the present invention will be described below.

FIG. 1 is a diagram illustrating an example of a manufacturing process for manufacturing product Sn and product Pb. As exemplified in FIG. 1, decopperization and carbonation are performed on lead raw materials such as lead slag and waste batteries generated in a copper smelting process or the like. The lead carbonate obtained by decoppering and carbonation is put into a Pb electric furnace as a Pb raw material. Lead carbonate is separated into crude Pb metal and slag by melting in a Pb electric furnace at 1000-1200°C.

Rough Pb metal contains Sn as an impurity. For example, the Sn grade in rough Pb metal exceeds 6.0 mass%, and may be 8.0 mass% or more. Since the process described below can effectively remove Sn, it is particularly effective when the Sn quality in the rough Pb metal exceeds 10.0 mass %.

The cooled crude Pb metal is charged into a Harris furnace. In the Harris furnace, the molten crude Pb metal obtained by melting the crude Pb metal is treated with soda. The soda treatment involves adding, for example, caustic soda to molten crude Pb metal heated to about 500° C., and optionally adding additional caustic soda and sodium nitrate to convert Sn into a soda salt (Na ₂ SnO ₃ ). It is a process that turns into a solid and solidifies on the surface of the molten metal. Solidified Sn soda salt is commonly referred to as Sn scum. Sn scum can be removed by scooping and separating the Sn scum. A series of steps including a step of soda treatment and a step of separating Sn scum are repeated one or more times in order to sufficiently lower the Sn grade in the molten crude Pb metal. A step of repeating the series of steps one or more times is called a Harris treatment step.

Sn scum is used as a Sn raw material for Sn production. Specifically, the Sn scum is subjected to a Sn leaching process for leaching Sn. The resulting post-leaching solution is subjected to an electrowinning step to produce product Sn. The leaching residue of the Sn leaching process is repeated to the lead electric furnace or carbonation process. On the other hand, the Harris treatment step yields refined Pb metal with reduced Sn grade. This purified Pb metal is subjected to an electrolytic refining process to produce product Pb.

FIG. 2 is a diagram illustrating the Harris treatment process. As illustrated in FIG. 2, cooled crude Pb metal is introduced into a Harris furnace 10 . By heating this crude Pb metal in a Harris furnace 10, a molten crude Pb metal 20 is obtained. For example, the Sn grade of the molten crude Pb metal 20 before soda treatment is 3.0 mass% or more. In addition, the black circle represents the Sn component contained. By soda-treating the molten crude Pb metal 20, Sn scum 30 is generated on the surface of the molten metal. The Sn scum 30 can be removed by separating the Sn scum 30 by, for example, scooping it with a net. Furthermore, by subjecting the molten crude Pb metal 20 to soda treatment, Sn scum 30 is generated on the surface of the molten metal. The Sn scum 30 can be further removed by separating the Sn scum 30 by, for example, scooping it with a net. In the Harris treatment process, the process of soda treatment and the process of separating the Sn scum 30 are repeated until the Sn concentration in the molten crude Pb metal 20 becomes sufficiently low. When the Sn concentration in the molten crude Pb metal 20 becomes sufficiently low, the refined Pb metal 40 can be recovered from the Harris furnace 10 by sucking the molten crude Pb metal 20 with a metal pump.

The Sn scum 30 includes both large particle size particles and small particle size particles. Therefore, it is conceivable to scoop up the Sn scum 30 using a small-mesh net. However, if a mesh with a small mesh size is used, the hot water is not easily drained, and impurities such as Pb may enter the Sn scum 30 . If the amount of impurities mixed into the Sn scum 30 is large, the number of repetitions of the impurities increases when the leaching residue of the Sn scum 30 is repeated in the lead refining process, which may increase the processing cost and deteriorate the yield. be.

The inventors paid attention to the grain size of the Sn scum 30 during the soda treatment. The present inventors have found that Sn scum 30 with a large grain size is generated in soda treatment, followed by Sn scum 30 with a small grain size. This mechanism is due to the large amount of Sn contained in the melted crude Pb metal 20 at the beginning of the soda treatment, so that many nuclei of the Sn scum 30 are generated and aggregated to coarsen the Sn scum 30. is presumed to be

Therefore, in the present embodiment, in the Harris furnace 10, a soda treatment step is performed in which the molten crude Pb metal 20 is treated with soda. and a removing step of removing Sn scum from the Harris furnace 10 by scooping it with a second net having a mesh smaller than that of the first net. This removal step is a step performed between the previous soda treatment and the next soda treatment.

In this case, when scooping the Sn scum 30 with the first net, the Sn scum 30 having a large grain size can be scooped with good hot water removal. Therefore, the Sn scum 30 can be recovered while suppressing the amount of impurities adhering to the Sn scum 30 . Therefore, contamination of the Sn scum 30 with impurities can be suppressed. Since the Sn scum 30 having a large grain size does not remain when the second mesh is used, the total amount of the Sn scum 30 is reduced. In this case, even if a second net with small mesh is used, the amount of impurities adhering to the Sn scum 30 is suppressed. From the above, the Sn scum 30 can be recovered while suppressing the amount of impurities mixed into the Sn scum 30 .

For example, the first net preferably has an opening of 3 mm to 5 mm. In this case, since the meshes of the first mesh are sufficiently large, the Sn scum 30 having a large grain size can be scooped out with good hot water removal. For example, the second net preferably has an opening of 1.5 mm or less. In this case, since the meshes of the second mesh are sufficiently small, the Sn scum 30 having a small particle size can be scooped, and the Sn scum 30 can be sufficiently recovered.

The Sn scum 30 is preferably scooped with the second net after being scooped with the first net a plurality of times. In this case, the second net is used after the Sn scum 30 having a large grain size is sufficiently scooped up by the first net. As a result, it becomes possible to further suppress contamination of the Sn scum 30 with impurities.

It is preferable to scoop the Sn scum 30 a plurality of times with the first net, and scoop the Sn scum with the second net after the first net cannot scoop the Sn scum. In this case, the second net is used after the Sn scum 30 having a large grain size is sufficiently scooped up by the first net. As a result, it becomes possible to further suppress contamination of the Sn scum 30 with impurities.

It is preferable that the Sn grade in the molten crude Pb metal 20 is reduced to 3 mass % or less during the period from scooping the Sn scum 30 with the first net until scooping the Sn scum with the second net. In this case, the second net is used after the Sn scum 30 having a large grain size is sufficiently scooped up by the first net. As a result, it becomes possible to further suppress contamination of the Sn scum 30 with impurities.

According to the method for removing Sn according to the present embodiment, since the Sn scum 30 is scooped up by the second net after the Sn scum 30 is scooped up by the first net, contamination of the Sn scum 30 with impurities can be suppressed. . Thereby, for example, the Pb content of the Sn scum 30 scooped by the first net and the second net can be made 20 mass % or less.

(Example)
Sn scum 30 was collected using a first screen and a second screen according to an embodiment. In the examples, the Sn grade in the molten crude Pb metal 20 before soda treatment was 5 mass % to 10 mass %. Sn scum 30 was generated by soda treatment, the Sn scum 30 was scooped with a first net with a mesh size of 5 mm, and then the Sn scum 30 was scooped with a second net with a mesh size of 1 mm.

(Comparative example)
In the comparative example, the Sn scum 30 was scooped using only one type of net without using two types of nets. The Sn grade in the molten crude Pb metal 20 before soda treatment was 5 mass % to 10 mass %. Sn scum 30 was generated by soda treatment, and the Sn scum 30 was scooped with a net of 1 mm mesh.

The amounts of Sn and Pb in the Sn scum 30 collected with a net were measured for the examples and the comparative examples. Table 1 shows the measurement results. As shown in Table 1, in the comparative example, the recovered Sn scum 30 had a low Sn quality and a high Pb quality. This is probably because only a mesh with a small mesh size was used, and hot water was not drained well when the Sn scum 30 having a large particle size was scooped up, and impurities such as Pb were mixed into the Sn scum 30 . On the other hand, in the example, the Sn quality in the collected Sn scum 30 was high and the Pb quality was low. This is because the large-mesh first mesh can scoop up Sn scum 30 with a large grain size well, and when the second mesh is used, the total amount of Sn scum 30 is reduced and impurities adhere to the Sn scum 30. It is thought that this is because the amount was suppressed.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the scope of claims. Change is possible.

10 Harris Furnace 20 Molten Crude Pb Metal 30 Sn Scum 40 Refined Pb Metal

Claims (8)

a soda treatment step of soda-treating molten crude Pb metal in a Harris furnace;
and a removing step of scooping Sn scum generated by the soda treatment with a first net with a larger mesh size and then scooping it with a second net with a smaller mesh size than the first net to remove the Sn scum. A Sn removal method characterized by: The first net has meshes of 3 mm to 5 mm,
2. The method for removing Sn according to claim 1, wherein said second mesh has meshes of 1.5 mm or less. 3. The method for removing Sn according to claim 1, wherein the Sn scum is scooped with the second net after being scooped with the first net a plurality of times. The method according to any one of claims 1 to 3, wherein the first net scoops the scum a plurality of times, and after the first net cannot scoop the scum, the second net scoops the scum. Method for removing Sn as described. 2. The quality of Sn in the molten crude Pb metal is set to 3 mass % or less during a period from scooping the Sn scum with the first net until scooping the Sn scum with the second net. 5. The method for removing Sn according to any one of -4. 6. The method for removing Sn according to any one of claims 1 to 5, wherein the Sn scum picked up by said first net and said second net has a Pb content of 20 mass% or less. The method for removing Sn according to any one of claims 1 to 6, wherein the Sn grade of the molten crude Pb metal is 3.0 mass% or more. Producing Pb by performing an electrolytic process on refined Pb metal obtained by removing Sn from molten crude Pb metal by the method for removing Sn according to any one of claims 1 to 7. A method for producing Pb, characterized by:

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